THE FISH PASS AT SIKFORS FUNCTION AND A PROPOSAL FOR THE ENTRANCE. O. Hammarberg. Luleå University of Technology, Luleå, Sweden ABSTRACT

Transkript

1 CASE STUDBES

2 THE FISH PASS AT SIKFORS FUNCTION AND A PROPOSAL FOR THE ENTRANCE O. Hammarberg Luleå University of Technology, Luleå, Sweden ABSTRACT This paper discusses the design of a fish ladder that was built in connection to the new hydroelectric dam in Piteålven, in During the five years that the ladder has been in operation die ladder has not been readily found by the migrating fish. The main purpose of this work has been to develop a proposal for a new entrance based, among other things, on measurements of water level fluctuations in the river downstream the dam. The suggested reconstruction includes an etension of the ladder and provision of auiliary water through the ladder floor. Dimensioning of the proposed entrance was made with empirical flow equations presented in the literature. INTRODUCTION Pitealven is one of the smaller mountain rivers in Sweden and is located just south of the polar circle, see Fig.. 1. The regulation dam consists of four spillways (see Fig. l and 2); one bottom spillway, one sector spillway and two segment spillways. The segment spillways are used most of the time. The minimum discharge over the regulation dam is in summer time 15 mvs. The fishway is a pool and weir type with 30 cm head between pools, discharge through the ladder is usually l mvs. Å1! B FSN D Fig. 1. Location of Pitealven and Sikfors power station. Al-Bottom spillway, A2 pool for water from Al, B-Sector spillway, C- Segment spillway, D- Segment spillway I-Fishway, H- "Entrance pool". 45

3 One difficult problem with the fishway is that the fish, Baltic salmon and sea trout, can be standing below the segment spillways for a long time before they eventually can be seen in the ladder. There have been eperiments to discharge water through the bottom spillway to attract fish towards the entrance. If this discharge has been larger than about l m 3 /s it seems like the fish is disturbed more than helped. Sometimes the fish has been swimming up in the pool below the bottom spillway instead of up in the ladder. Fig. 2. The pool and weir fishway at Sikfors. This photo was taken from the right bank. Even when the dam is operated so that the "velocity barrier" forms a diagonal lead towards the left bank, see Fig. 3., it seems like the fish is delayed. It is not so strange that the fish swims towards the main flow because they usually do. Upstream limit of migration Hydraulic jump Search pattem Flow direction Fish Fig. 3. Schematic plan of adjusted dam operation. It can be easier for the fish to find the entrance if this is placed as close as possible to the point to which the migrating fish penetrate farthest upstream at an obstruction (Clay 1995). The work to develop a proposal for a new entrance for the fishway at Sikfors were made as a Master Thesis at Luleå University of Technology in the winter and early spring 1997 (Hammarberg 1997). 46

4 A PROPOSAL FOR THE ENTRANCE To overcome some of the problems a proposal for a new entrance were developed. In this proposal the entrance were placed closer to the segment spillways, see Fig 4. To be able to etend the ladder and still get enough water velocities the fbllowing were proposed: 1. To weirs, that are placed in comers, can be tåken away, see fig The fishway walls and the weirs in the lower part need to be bigher. 3. Auiliary water can be added through the ladder floor. 4. The entrance weir has to be adjustable. Fig. 4. Schematic plan over the etended entrance. Orifices are suggested in the last weirs to make it easier for fish, swirnming at different levels, in the water column, to find the entrance. An alternative to this could be to build two different entrances. It is important to be aware of that salmon and sea trout otten are swirnming at different levels. Dimensioning criteria Water velocities out from the fishway entrance should be between 1,2-2,4 m/s. Minimum depth over the entrance weir is 0,6 m. Minimum velocity in a submerged section of the fishway is 0,6 m/s. Maimum velocity through the diffusion grating is 0,15 m/s. Water flow in the ladder should not change between plunging and streaming mode. As får as it was possible, and practical, the entrance should have the same dimensions as the other part of the fishway. Most of the dimensioning criteria were found in "Design of Fishways and other fish facilities" (Clay 1995). Calculations and dimensioning were made so that the criteria could be fulfilled when the water level is fluctuating between values that are normally obtained in Sikforsen during the mlgration period. These values were obtained from measurements done by Vattenfall AB. The calculations were performed with the equations presented in the papers "Plunging and streaming flow in pool and weir fishways" (Rajaramam et al 1988), "Pool-orifice and poolorifice-weir fishways" (Rajaramam and Katopodis 1989) and "Submerged flow regimes of rectangular sharp-crested weirs" (Rajaramam and Wu 1996). RESULTS The proposed entrance is shown in the schematic plans in Fig 5. 47

5 A-A C-C Rcgul.ition / _=_n Fish pass JUUUUU' Rcgulntion gate DifTmion chamber Fig. 5. A-A Longitudinal section through the proposed entrance. C-C Cross section through the diffusion system. DISCUSSION The presented proposal is just one of many which could make the fishway at Sikfors more effective. Maybe more than one entrance is needed. If the natural reproduction of salmon and sea trout should be able to increase in Pitealven I think that a smolt bypass system at the intake channel is advisable. Maybe could water from this bypass be used as attraction water at the fishway entrance. REFERENCES Clay, C. H., Florida. Design of Fishways and other fish facilities, 2 nd edition. CRC Press Inc, Hammarberg, O., 1997.Fisktrappa vid Sikfors kraftverk, Funktionsbeskrivning och forslag till ny ingångskonstruktion. Luleå University of Technology. Master Thesis 1997:264 CIV. ISSN Rajaratnam, N., Katopodis, C., Mainali, A., 1988, weir fishways. J. Hydraulics Eng. 114: Plunging and steaming flow in pool and Rajaratnam, N., Katopodis, C.,1989. Pool-orifice and pool-orifice-weir fishways. Can. J. Civ. Eng Rajaratnam, N., Wu, S., Submerged flow regimes of rectangular sharp-crested weirs. J. Hydraulics. 122(7):

6 REGULERINGEN, METODER OG MATERIALE Hunderfossen kraftverk ligger 15 km fra Lågens utløp i Mjøsa, har en fallhøyde på 46 m, og den totale slukeevnen i kraftverket er 300 m 3 /s. Etter at vannet har passert turbinene ledes det tilbake i Lågen ca. 4,4 km nedenfor Hunderfossen gjennom en tunnel. På denne elvestrekningen er det minstevannføring på 2 m 3 /s i vinterperioden oktober-juni, mens det i Hunderørretens viktigste gytevandringsperiode (juli og august) er 20 m 3 /s. I løpet av siste del av oppvandringsperioden, i september, trappes minstevannføringen ned til 2 m 3 /s. Demningen ved Hunderfossen er ca. 200 m bred og består av 6 flomluker, l tømmerluke og l isluke (Fig.l). Vanligvis slippes overskuddsvann som bunnvann gjennom flomlukene. Isluka kan benyttes til slipping av inntil 40 m 3 /s overflatevann, mens tømmerluka som også gir overflatetapping, benyttes sjelden, og bare ved stor, vedvarende flom. I perioden ble totalt 131 ørreter (2-12 kg) fanget enten i fisketrappa eller i høler nedenfor fossen. De ble påsatt eksterne radiosendere og enten satt ut nederst i Lågen eller ovafor Hunderfossdammen for å Kraftverk Fig. 1. Skisse over demningen ved Hunderfossen kraftverk. Map of the Hunderfossen dam and power plant. teste oppvandring i forhold til vassføring og temperatur, og nedvandring etter gyting. I 1997 ble 25 storørreter merket og sluppet ovafor dammen. For å undersøke nedvandring av smolt om våren, ble det benyttet 2- årig smolt (20-25 cm) fra Hunderfossen settefiskanlegg. 10 smolt ble radiomerket og fulgt på vandring mellom Hundefossen og Mjøsa i 1993, mens 25 smolt ble radiomerket for studier av utvandring over dammen i Vandringene til både vinterstøing og smolt ble fulgt ved manuell peiling fra bil, og ved automatiske dataloggere. For å teste utvandring av vinterstøing og smolt ved ulike vannslipp, ble det sluppet bunnvann gjennom flomlukene og suksessivt økende overflatetapping (0-40 mvs) gjennom isluka. I fisketrappa gikk det hele forsøksperioden 1-2 m 3 /s. RESULTATER OG DISKUSJON Gytevandring og nedvandring etter gyting For resultatene av studier på gytevandring og bruk av lokkeflommer henvises til Arnekleiv & Kraabøl (1996). Her gjengis kort en oppsummering av resultatene: Ørretene vandret raskt opp til samløpet mellom elva og tunnellutløpet. Ved minstevannføring på regulert strekning (< 20 m 3 /s) stoppet videre oppvandring og ørretene oppholdt seg i perioder inne i avløpstunnelen. Enkelte snudde og fant gyteplass lenger ned i elva Ved økende vannføring fortsatte oppvandringa på minstevannstreknmgen opp til gyteplasser nedafor fossen eller til fisketrappa. Når fiskene klarte å passere tunnelutløpet, kunne de vandre på vannføring helt ned til 5 m 3 /s på minstevannstreknmgen. 50

7 OPP- OG NEDVANDRING AV ØRRET VED HUNDERFOSSEN KRAFTVERK UPSTREAMAND DOWNSTREAM MIGRATIONS OF BROWN TROUTAT THE HUNDERFOSSEN POWER PLANT Jo Vegar Arnekleiv 1 og Morten Kraabøl 2 1 Norwegian University of Science and Technology, The Museum, Freshwater Ecology and Inland Fisheries Laboratory (LFI), N Trondheim, Norway 2 Miljøtjenester, Storgata 91, N Lillehammer, Norway ABSTRACT The spawning migration and the smolt migration of brown trout (Salmo trutta) in relation to water flow and temperature were analyzed by radio telemetry in the regulated River Gudbrandsdalslågen. Both spawning migration in autumn and postspawning migration down the river to Lake Mjøsa are affected by the river regulation undertaken at Hunderfossen. The minimum water discharge (2-20 m 3 /s) downstream the dam prevented the ascent of brown trout to pass the outlet of the tunnel. Eperiments, using attraction water, resulted in significantly increase m upstream migration. After spawning in the headwaters above the dam, trout migrated downstream in winter/early spring at low temperatures, but were unable to pass the dam due to low water discharge. Periods of top water release of > 10 m 3 /s at temperatures > 2 C made trout passing the dam and migrating downstream. Also, we found a good correlation between top water release and smolt migration. Of 25 radiotagged smolt, none passed the turbines, but they all migrated over the dam. INNLEDNING Hunderørreten er en storvokst ørretstamme som lever sine første 2-6 år i Gudbrandsdalslågen (heretter kalt Lågen) før den smoltifiserer ved en gjennomsnittslengde på 25 cm. Utvandring til Mjøsa, Norges største innsjø, skjer om våren/forsommeren, og fisken skifter raskt diett frå insektlarver til fisk. Den får en rask vekst og oppholder seg gjennomsnittlig tre år i innsjøen før kjønnsmodning og gytevandring tilbake i elva. Normalt er det to år mellom hver gytevandring (flergangsgyter), og gytefiskens gjennomsnittsvekt er snaut 4 kg. Nesten årlig fanges eksemplarer på kg på stang. Som i de fleste regulerte vassdrag med vandrende fiskepopulasjoner er det i Hunderfossen bygd fisketrapp. Denne har relativt god virkning på middels vassføring, men dårligere på høy og lav vassføring (Jensen & Aass 1991, 1995). Likeså har forsøk med radiotelemetri vist at gytevandrende ørret har problemer med å passere tunnelutløpet frå kraftverket under gjeldende minstevannføring (Arnekleiv & Kraabøl 1996). Mens det er gjort flere undersøkelser på gytevandring oppover vassdraget, finnes det lite data på åtferd og nedvandring etter gyting. For Hunderørreten, hvor individene ofte er flergangsgytere, er det viktig at fisken kommer ut i innsjøen igjen etter gyting. Flere av de store gytefeltene til Hunderørreten er lokalisert ovafor Hunderfossen (Arnekleiv & Kraabøl 1994, 1996, 1998). En stor mengde ørretsmolt vil derfor måtte passere demningen på sin veg ned til Mjøsa om våren/forsommeren. I denne undersøkelsen har vi ved hjelp av radiotelemetri studert hvordan utvandring av vinterstøing og smolt av Hunderørret foregår over Hunderfossen dam i forhold til vannslipp over dammen. Kan manøvrering av kraftverket benyttes for å lette utvandringen? 49

8 Lokkeflommer på 60 m 3 /s i ett døgn medførte at % av fiskene som stod i samløpet fortsatte oppvandringen, mens lokkeflom på 30 m 3 /s ga minimal oppvandring. Ørret som ble sluppet ovafor dammen vandret raskt direkte opp til gyteplass, 4-54 km oppover Lågen. Gyteområder og gyteperiode ble kartlagt ved hjelp av radiomerket fisk. Etter gyting ovafor fossen, ble 62,5 % av de radiomerkete fiskene registrert ved demningen i Hunderfossen i november og desember På denne tida ble det kun tappet vann (2 m 3 /s) gjennom fisketrappa. Fiskenes åtferd var preget av stor aktivitet, både i form av hyppige aktivitetsutslag på radiosenderne og bevegelsesmønster, til tross for vanntemperaturer på 0,1-0,8 C (Fig.2). Imidlertid ble det ikke registrert videre nedvandring forbi dammen (i fisketrappa) i løpet av høsten og vinteren. De resterende gytefiskene vandret fra gyteplassene/overvintringsstedene i elva og til Hunderfossen på våren, ved totalvannføring på opp mot 700 m 3 /s og vanntemperatur på 5-6 C. Både fiskene som vandret ned fra gyteplassene på høsten og fiskene som kom ned under begynnende vårflom samla seg etterhvert ved damkrona hvor de vandret fram og tilbake, men ble hindret i videre nedvandring selv om det ble sluppet betydelige vannmengder som bunnvann gjennom flomlukene (Fig. 3). Først når lukene ble åpnet helt opp skjedde nedvandring forbi dammen, og det ble registrert nedvandring både om dagen og natten. Det var en klar sammenheng mellom tapping av mye overflatevann og utvandring av vinterstøing, mens det ikke ble registrert nedvandring ved tapping av bunnvann eller små mengder overflatevann gjennom isluka og fisketrappa (< 8 m 3 /s) Nov. Deo Fig. 2. Bevegelsesmønster for tre av de 16 ørretene i demningsbassenget ovenfor Hunderfossen i perioden 24. november 1993 til 5. juni Movements of three brown trout near the Hunderfossen dam in the period Nov June I 1997/98 ble det testet om overflatetapping gjennom isluka (inntil 40 m 3 /s) kunne få vinterstøingen til å passere dammen. I oktober passerte 3 radiomerket fisk dammen ved å vandre ned fisketrappa. Dette er en av få observasjoner av nedvandring via fisketrappa. Under forsøk med vannslipp gjennom isluka (4-8 m 3 /s) i november vandret ytterligere 2 av de 25 ørretene ned forbi dammen ved 1,5 C. Økende vannføring og vannslipp gjennom flomlukene på våren medførte ikke noen nedvandring, men ved slipping av inntil 40 m 3 /s overflatevann gjennom isluka i tre perioder i mai og juni, passerte de resterende overlevende vinterstøingene dammen (Fig.4). Resultatene indikerer at utvandring av vinterstøinger hindres ved Hunder fossdammen. Forsøkene viser at lukemanøvrering kan ha stor betydning for at storørreten kan passere Hunderfossdammen på nedvandring etter gyting. Sannsynligvis vil en tidlig nedvandring fra gyteplassene og til Mjøsa bety økt overlevelse for individene ved at de raskt kommer 51

9 tilbake til innsjøen med mye forfisk til stede. Registreringene etter gyting tyder på at % av Hunderørreten som gyter ovafor fossen starter nedvandringen på høsten og kunne overvintret i Mjøsa dersom ikke utvandringen ble hindret. Water 11-, temperature "O 9-8- SpBwater 600 m a /s Fig. 3. Utvandring av vinterstøing over demningen i forhold til vannføring, manøvreringen av flomluke l og vanntemperatur. Postspawning migration of brown trout at the Hunderfossen dam in relation to water discharge at water temperature Nov July O CO <D O> t- CM OJ CM OJ Mal Juni Fig. 4. Utvandring av vinterstøing av Hunderørret over dammen våren 1998 i relasjon til temperatur og vannføring. Downstream migration of postspawning brown trout at the Hunderfossen dam in 1998 in relation to water temperature and water discharge. 52

10 UTVANDRING AV ØRRETSMOLT Et pilotforsøk med 10 radiomerkete smolt satt ut nedafor Hunderfossdammen viste at de brakte i gjennomsnitt 11,5 døgn (variasjon 2-21 døgn) på vandringen ned til Mjøsa (15,2 km). De vandret langt raskere på den langsomtflytende nederste elvestrekningen (10,8 km) sammenlignet med regulert elvestrekning med stort fall (tabell 1). Dette kan ha sammenheng med økt predasjonsrisiko i de nedre deler av elva hvor det er en tett bestand av gjedde (Eso lucius). Det er i andre undersøkelser registrert stor mortalitet hos vandrende smolt fra predatorfisk i estuarier (Hvidsten & Møkkelgjerd 1987, Hvidsten & Lund 1988, Jepsen et al. 1998), og det er funnet Carlinmerket smolt av Hunderørret i gjeddemager fra Lågendeltaet (Jan Teigen pers. medd.). De radiomerkete smoltene startet nedvandringen på økende eller høy vannføring. Det var god korrelasjon mellom økning i vannføring og smoltutvandring ved en temperatur på 5,4-7,5 C (Fig. 5). c f s O LOKALITET Hunderfossen- Andershølen Ensbyhølen Hølsauget Fåberg Mjøsa MAI JUNI Fig. 5. Smoltvandring fra Hunderfbssen i relasjon til temperatur og vannføring. Smolt migration in relation to water temperature and water discharge. 53

11 Table 1. Smoltens gjennomsnittlige vandringshastighet på ulike elvestrekninger. The average speed of smolt descending the different river stretches * kroppslengde pr. sekund (body length per sec.) Elvestrekning Lengde (km) Fallhøyde (m) Hastighet (kl s" 1 )* Hunderfossen-Hølsauget Hølsauget-Mjøsa 4,4 10, ,02 0,29 Totalt 15,2 42 0,06 I Hunderfossen kan ørretsmolten passere enten gjennom lukene i dammen eller gjennom turbinene i kraftverket. Det er tidligere vist at laksesmolt kan passere Kaplanturbiner uskadd ved fallhøyder opptil 100 fot (ca. 33 m) (Bater 1961). Det er også gjort forsøk med utsetting av smolt gjennom turbinene i Hunderfossen med relativt godt resultat (Aass 1976). Det er imidlertid usikkert om smolten normalt vil slippe seg ned trykksj aktene ved manglende utvandringsmulighet over dammen. Det ble derfor utført et tilsvarende forsøk som med vinterstøing våren 1998 med vannslipp over isluka. Forsøkene viste at den radiomerkede smolten holdt seg i inntaksmagasinet ved tapping av bunnvann. Det ble ikke registrert utvandring hverken gjennom fisketrappa eller turbinene. Ved tre forsøk med overflatetapping over isluka i mai og juni, passerte alle de 25 ørretsmoltene dammen (Fig. 6). 64 % av smolten vandret ut ved første overflatetapping. Det ble funnet en sterk korrelasjon mellom vannføringsøkning, overflatetapping og utvandring av smolt. Undersøkelsen indikerer at ørretsmolten normalt ikke vandrer gjennom kraftverket, men passerer dammen ved overflatetapping, sannsynligvis i forbindelse med vårflommen i juni/juli. Forsøkene indikerer videre at smolten er vandringsklar allerede i mai, men at videre utvandring sannsynligvis hindres når det ikke slippes overflatevann T, ant smoltut lo temperatur 100 vf over dam vf isluka l l 11 l l l l 11 l l l li T 11 l 11 l l l l Mai Juni Juli Fig 6. Utvandring av ørretsmolt over dam Hunderfossen i relasjon til temperatur og vannføring. Smolt migration at the Hunderfossen dam in relation to water temperatur e and water discharge. 54

12 TAKKSIGELSER Disse undersøkelsene er utført i perioden med økonomisk støtte fra flere instanser: Energiforsyningens Fellesorganisasjon (EnFO), Norges Vassdrags- og Energiverk (NVE), BBV-programmet i Oppland (regulanter m.fl.), Direktoratet for naturforvaltning (DN), Fylkesmannen i Oppland - miljøvernavdelinga og Lågen Fiskeelv. K/L Opplandskraft har gitt avgjørende hjelp i form av fleksibel lukemanøvrering i forsøksperiodene, og de ansatte i kraftstasjonen har bidratt med verdifulle observasjoner. Personalet ved Hunderfossen settefiskanlegg har vært behjelpelige under radiomerking av både voksen fisk og smolt. Det rettes en takk til alle som har bidratt i prosjektet. REFERANSER Araekleiv, J.V. & Kraabøl, M Gytevandring til innsjølevende aure i Gudbrandsdalslågen og Nea. I: Erlandsen, A. H. (red). Fiskesymposiet Energiforsyningens Fellesorganisasjon, s Arnekleiv, J.V. & Kraabøl, M Migratory behaviour of adult fast-growing brown trout, Salmo trutta, in relation to water flow in a regulated Norwegian river. - Regulated Rivers, Research & Management. Vol. 10: Arnekleiv, J.V. & Kraabøl, M Utvandring av vinterstøing og smolt av Hunderørret forbi Hunderfossen. EnFO, Fiskesymposiet Publikasjon nr : Bater, G River utilization and the preservation og migratory fish life. - The North of Scotland Hydro-Electric Board. Paper no. 6471, pp Hvidsten, N. A. & Møkkelgjerd, P Predation on smolts, Salmo salar, in the estuary of the River Surna, Norway. - Journal of Fish Biology 30: Hvidsten, N. A. & Lund, R. A Predation on hatchery-reared and wild smolts of Atlantic salmon, Salmo salar, in the estuary of River Orkla, Norway. - Journal of Fish Biology 33: Jepsen, N., Aarestrup, K. & Rasmussen, G Survival of radiotagged Atlantic salmon (Salmo salar L.) and trout (Salmo trutta L.) smolts passing a reservoir during seaward migration. Nordic Conference on Fish Passage, Proceedings: -. Jensen, A. J. & Aass, P Oppgang av ørret i fisketrappa i Hunderfossen i forhold til vannføring ov vanntemperatur. - NINA forskningsrapport 19,27 s. Jensen, A. J. & Aass, P Migration of a fast-growing population of brown trout (Salmo trutta) through a fish ladder in relation to water flow and water temperature. - Regulated Rivers, Research & Management. Vol. 10: Kraabøl, M. & Aass, P Stangfisket etter Hunderørret nedenfor Hunderfossen Fylkesmannen i Oppland, miljøvernavdelingen. Rapport nr. 3,1995,27 s. Aass, P Utsettinger av Hunderørret Direktoratet for vilt- og ferskvannsfisk. Fiskeforskningen. Notat 14. mai Aass. P Utsetting av Hunderørret i Mjøsa og Lågen Fylkesmannen i Oppland, miljøvernavdelingen. Rapport nr. 9,1990,25 s. 55

13 LAKSETRAPPENE ILÆRDALSELVA ERFARING FRA DRIFT Leif M. Sættem Møre og Romsdal County Department of the Environment, Fylkeshuset, N-6400 Molde, Norway ABSTRACT Four pool and weir ladders were constructed during hydroelectric regulation of the River Lærdal, Sognefjorden, South Norway. The lowest ladder (Sjurhaugfoss, 25 km from the mouth) and the uppermost one (Svartegjelfoss, 31 km) are in tunnels. Lights are installed in the Sjurhaugfoss tunnel. Both have counters recording upwardmigrating fish larger than 50 cm. The ladders made an additional 16 km available to spawning salmon and sea trout. The run to these new stretches mainly occurs from mid-july to the end of September. An average of 377 upward-migrating fish were recorded annually at Sjurhaugfoss in , the highest number bemg 867 in Whether the fishway at Sjurhaugfoss is illuminated or not seems to have no influence on whether fish enter it, but the migrating speed of fish already in the tunnel is sometimes affected when the light is switched on. INNLEDNING Lærdalselva er en ettertraktet sportsfiskeelv. Årlig innrapportert totalfangst av laks og sjøaure har vært oppe i 20 tonn (1974). Elva er regulert ved bygging av Borgund Kraftverk i 1974 og Stuvande Kraftverk i forbindelse med kraftreguleringen er det bygget fire laksetrapper (Sjurhaug-, Husum-, Kolgryte- og Svartegjelfoss). OMRÅDEBESKRIVELSE Lærdalsvassdraget (1.184 km 2 ) munner ut ved Lærdal i indre del av Sognefjorden i Sør- Norge (Fig. 1). Vassdraget har en årlig middelvannføring på 36 m 3 /s og vanntemperaturen kan komme opp i 15 C. Tradisjonell strekning for anadrom fisk på gytevandring er til Sjurhaugfoss, 240 m.o.h. og 25 km fra munningen (Fig. 1). Innsiget av laks til munningen av Lærdalselva skjer i siste halvdel av mai. Fiskevandringen de første 20 km opp til Seltagelet (Fig. 1) er lite påvirket av årlige variasjoner i vanntemperatur og vannføring. Laksen ankommer under gjelet i slutten av juni til begynnelsen av juli (Sættem 1991). Vandringen opp Seltagjelet er derimot sterkt påvirket av vannføring og -temperatur. Kaldt vann og høy vannføring stopper den videre vandringen og i enkelte år tar det nær en måned å passere. Den videre vandringen opp til og med laksetrappen i Sjurhaugfoss tar i gjennomsnitt omlag en uke. 56

14 m above sea level HEGGFOSS SOGNEFJORDEN km from outlet outlet 25 Fig. 1. River Lærdal in profile. Fisketrappen forbi Sjurhaugfoss ligger i tunnel og er 195 m lang med 32 kulper og en samlet høydeforskjell på 16 m. I Husumfoss er trappen 70 m lang med 12 kulper og en høydeforskjell på 6 m. Fisketrappen i Kolgrytefoss er 90 m lang med 18 kulper og en høydeforskjell på 9 m. Trappen i Svartegjelfoss går i tunnel og er 130 m lang med 26 kulper og en samlet stigning på 13 m. Frå Svartegjelfoss til stopp lakseførende strekning ved Heggfoss (432 m.o.h. og 41 km frå munningen) er det relativt rolige elvestrekninger. Trappene i Sjurhaugfoss og Svartegjelfoss er utstyrt med elektroniske fisketellere. Disse måler forandring i elektrolyttisk ledningsevne når fisken passerer gjennom et pleksiglassrør. I tillegg er det montert små spotligths i tunneltaket rett over deleveggene. Disse lyser oppstrøms mot neste delevegg og det antas at det ikke blir noen blendvirkning for oppvandrende fisk (Romundstad 1991). METODE OG MATERIALE All oppvandrende fisk større enn cm ble registrert i telleapparatene i Sjurhaugfoss og Svartegjelfoss i perioden Tilsammen ble det registrert fisk i Sjurhaugfoss og i Svartegjelfoss. Dette tilsvarer et årlige gjennomsnitt på 377- og 103 fisk over 16 år. RESULTATER Det har vært store variasjoner i antallet fisk gjennom telleapparatet i Sjurhaugfoss. Den største mengden ble påvist i 1982 med 867 fisk (Fig. 2). Det laveste tallet ble registrert i 1993 med 141 fisk. De fleste fiskene i Svartegjelfoss ble registrert i 1988 med 261 (Fig. 2). Den store oppvandringen gjennom laksetrappen i Svartegjelfoss i 1988 kan settes i sammenheng med den raske passeringen av Seltagjelet (6 døgn) på grunn av lav vannføring av temperet vann. I 1987 fant vi det motsatte bildet med høy vannføring og kaldt vann som resulterte i sen passering av Seltagjelet (25 døgn) og med påfølgende liten oppvandring gjennom trappen i Svartegjelfoss (Sættem 1991). 57

15 1000 -i D Sjurhaugfoss Svartegjelfoss O l l [L Fig. 2. Annual number of salmon and sea trout ascending the Sjurhaugfoss and Svartegjelfoss fish ladders, River Lærdal, De fleste fiskene passerte Sjurhaugfoss frå slutten av juli til begynnelsen av september med den mest intense oppvandringsperioden i midten av august (Fig. 3). I Svartegjelfoss vandret de fleste fiskene fra begynnelsen av august til midten av september (Fig. 3). Oppgangsaktiviteten var størst til visse tider av døgnet. Hovedmengden av fisk vandret mellom kl. 17 og kl. 22 (Fig. 4) O _ n 0. D Sjurhaugfoss Svartegjelfoss l l l l l l llin.n-n _ Fig. 3. Weekly numbers of salmon and sea trout ascending the Sjurhaugfoss and Svartegjelfoss fish ladders, River Lærdal, Det ble ikke avdekket noen virkning av oppgang inn i trappen ved ulik bruk av lys i tunnelen i Sjurhaugfoss. Dersom laksetrappen lå i mørke noen dager og lyset ble tent, kunne det imidlertid registreres en økning i vandringshastigheten på fisk som allerede var i trappen (Romundstad 1991). 58

16 20 -, august 5 - O i im *. s. *^ Ittl lui tåmå - taum. ""i Tir-ii, BBM iimn KHH.!». msm """T -. lua inain, luti. 10 -i 5 O t 1 september Fig. 4. Hourly ascents of salmon and sea trout through the Sjurhaugfoss ladder, august and september OPPSUMMERING Fire fisketrapper har forlenget laks- og sjøaureførende strekning i Lærdalselva frå 25 til 41 km. Seltagjelet (20 km frå munningen) representerer et vanskelig elveavsnitt for fiskevandring og forholdene i vannføring og -temperatur bestemmer omfanget av den videre oppvandring gjennom trappene til de øvre elveavsnittene. I årlig gjennomsnitt ( ) er det registrert 377 fisk i fisketrappen i Sjurhaugfoss og 103 fisk i trappen i Svartegjelfoss. De fleste fiskene vandret i trappene i august og september og den høyeste aktiviteten i døgnet ble påvist frå kl Ulik bruk av lys i trappetunnelen syntes generelt å ha liten betydning for oppvandringen av fisk. TAKKSIGELSER Det rettes en stor takk til Arnt T. Romundstad, Borgund Kraftverk, som har stått for de årlige registeringene av fiskevandringen i trappene. Videre vil jeg rette en takk til Nils Lysne, Borgund Kraftverk, som har vært behjelpelig i befaring av trappeanleggene. REFERANSER Sættem, L.M Oppvandring av laks og fordeling av gytefisk i Lærdalselva og andre vassdrag i Sogn, s i Krogh, F.E. og Sættem, L.M. (red.) Villaksseminaret Kompendium, Lærdal 31. mai -1. juni Romundstad, A.T Biologiske og fiskeøkonomiske forutsetninger for fisketrapper. Norske erfaringer, s i Krogh, F.E. og Sættem, L.M. (red.) Villaksseminaret Kompendium, Lærdal 31. mai- l.juni

17 SALMON AND TROUT PASSAGE IN THE ISOHAARA FISHWAY, NORTHERN FINLAND AnneLaine University of Oulu, Department of Biology, P.O. Bo 333, Fl Oulu, Finland ABSTRACT The migratory fish stocks of the regulated River Kemijoki are maintained by stockings at the river mouth and at the nearby sea area. A fishway, built in connection with the enlargement of the Isohaara hydropower plant in 1993, opened a river stretch of 20 km for fish returning from sea migration. Almost a thousand adult salmonids passed through the Isohaara fishway during its first three years of operation. Although trout were large, up to 7 kg, the maimum weight of salmon was only 4 kg. The fishway discharge was increased, the vertical slots widened and a guiding fence installed at the southern entrance in In 1997, pools and a waterfall were applied in the northern entrance, to replace the previous Denil section. These changes increased the number of salmon and especially that of large salmon but did not affect the passage of trout. INTRODUCTION The River Kemijoki in northern Finland used to be one of the most productive salmon rivers of the Baltic sea area (Fig. 1). The first dam, Isohaara, was constucted close to the river mouth in About ten years later, the unique Kemijoki salmon was etinct. Today, the migratory stocks of this river are maintained by stocking salmon, trout and migratory whitefish at the river mouth or the nearby sea area. At the river area, non-migratory fish species or stocks are favoured. These include brown trout and rainbow trout. The Isohaara dam is 200 rn wide with one powerhouse at each shore. In connection with the new powerhouse, taken into use in 1993, a fishway was constructed primarily to enlarge the fishing area of salmon. By the fishway, a river stretch of 20 km was opened for the migratory fish. It consists of a basin without proper spawning areas. This paper describes the problematics of salmon and trout passage and the efforts of improving it in the Isohaara fishway during a si-year study. Fig. 1. The River Kemijoki with the location of Isohaara and other dams. 60

18 THE ISOHAARA FISHWAY The Isohaara fishway (Fig. 2) has two entrances with only one of them opened at a time. The southern entrance is of vertical slot type and it leads into a tunnel. The northern entrance starts as a Denil fishway and continues as an uncovered vertical slot fishway. These two sections join in the junction pool, and the fishway continues as a vertical slot fishway. The upper part of the fishway, with a deeper slope, is of Denil-type. The length of the fishway is 230 meters and the rise 12.5 meters. The design flow of the fishway was 0.5 m 3 /s with an almost equal auiliary flow at the southern entrance. Financial reasons have håd a great effect in determining the discharge because the promoter and the owner of the fishway, the municipality of Keminmaa, has to pay the power company for the water that runs through the fishway. Fishway eit Enlargement of the power Plant Fishway entrances Fig. 2. Layout of the Isohaara fishway: l, southern entrance; 2, northern entrance; 3, junction pool; 4, fish gathering and counting facilities PASS AGE PROBLEMATICS DURING THE FIRST THREE-YEAR PERIOD During the first three years of operation, ahnost a thousand salmonids passed through the fishway, when the quite numerous 2- and 3-year-old stocked salmon and trout are ecluded (Fig. 3). Salmon formed 60 %, trout 32 % and rainbow trout 8 % of the total. All rainbow trout originated from stockings in the basins above and salmon from stockings at the river mouth and the nearby sea area. Trout, on the contrary, håd been stocked botn up- and downstream from the Isohaara dam. Although trout passing through the fishway were large, up to 6-7 kg, the maimum weight of salmon was only 3-4 kg. Large salmon were, however, observed close to the fishway entrance and caught downstream from the fishway with nets. In the river downstream from the dam, there are up to nets per day, with a concentration of nets close to the fishway entrance starting from the 100-meter limit. Net fishing impedes the proper function of the fishway but is maintained because stocking migratory fish is meant for compensating the losses caused by hydropower construction only at the sea area and the river mouth, whereas the river area has compensations of its own. Large salmon were also regularly caught at the old powerhouse, where fish samples are collected for stock assessment and disease control purposes. At the old powerhouse, there is an ideal gathering area and due to a constant flow of 5 m 3 /s from a small turbine the salmon stay there even when the main turbines are closed. There is no respective attraction flow with a continuous character at the new powerhouse. 61

19 The daily numbers of salmon in the gathering pool of the fishway were positively related with the headwater level (Laine et al. 1998), indicating the importance of an adequate fishway discharge for sahnon. This was given etra support from the total lack of large, multi-seawinter salmon during the first three years. Trout, on the contrary, showed no similar preferences in respect to the headwater level. IMPROVING THE PASSAGE OF SALMON IN THE FISHWAY In 1996, the fishway discharge was increased, the vertical slots were widened, and a guiding fence installed at the southern entrance. That summer, the first large salmon passed through the fishway (Fig. 3). In spite of this, continuous observations were made of schools of large salmon 2-3 meters downstream from the entrance. 800 n co ^ o 15 co 400- D Rainbow trout H Brown trout M Salmon 3-4 kg kg kg CD -Q 3 z 200 O * Fig. 3. Yearly numbers of adults salmonids in the Isohaara fishway and the maimum weight of salmon for each year. The 1998 bar shows the number of salmonids by the early September. In the late summer 1997, the Denil-chute was removed from the northern entrance and replaced by pools forming a waterfall below the entrance. A guiding fence was installed also at this entrance. The underwater videos revealed that after these changes, salmonids, including large salmon, started to enter the fishway without delay when the powerhouse turbine flows were favourable. The salmonids were no longer seen to gather close to the entrance as they used to do earlier. During these two years, the numbers of salmon entering the river were high, but river fishing was more effective in 1997 than in hi 1998, the river migration was smaller, but despite of that, the fish numbers and the size of salmon entering the fishway increased from the previous years (Fig 3). Trout numbers have remained at an almost constant level each year. The percentage of trout is unepectedly high in the fishway when compared to the respective percentages in the catches both in the river, at the nearby sea area, and at the old powerhouse. Based on these observations, it is probable that the trout are more efficient in locating the fishway and entering it than salmon under a variety of environmental circumstances. 62

20 CONCLUSIONS The proportion of trout in the fishway is higher than epected, and the changes that have been made in the fishway have håd no discernible effects on trout passage. The fishway may be more suitable for trout than for salmon. The responses can also be eplained by the differences in the origin of trout and salmon; the trout returning from sea migration include those that have initialry been stocked in the river. Salmon, on the contrary, represent a population that is stocked downstream from the fishway and is etensively harvested by river fishing. For them, the situation is far from being optimal as comes to entering the fishway. Thus, for salmon, and especially for salmon of a hatchery origin and without a previous eperience from the river environment, intense stimuli at the fishway entrance are of utmost importance. REFERENCES Laine, A., Kamula, R. & Hooli, J Fish and lamprey passage in a combined Denil and vertical slot fishway. - Fisheries Management and Ecology 5:

21 Fishway in Halistenkoski Rapids on the Aurajoki River, S W Finland Juha Kååriå Environmental Office, City of Turku, Limankatu 61, FIN Turku, Finland juha.kaaria@turku.fi ABSTRACT A fishway in Halistenkoski rapids was opened in May The fishway features 22 basins with total head being 5.5 m. The fishway is equipped with a tracking system which helps to determine the quantity and size of the fish swimming in it. A total of 16 fish species have been found in the fishway, and 332 adult sea trout and 36 adult salmon have been controlled by means of the fishway in The presentations of fishway operations benefit tourism and research as well as educational purposes, and more than visitors have acquainted themselves with the fishway during the first three years. More information from the project is available in INTRODUCTION The Aurajoki River (drainage area 885 km^ ) in SW Finland is 70 km long, with a mean flow of 8.5 m 3 s~ l (Pitkånen 1994); in the whiter and summer, however, there is scarcely any flow at all. During the spring and autumn, the peak flows may rise up to a maimum of 286 m 3 s~l. Degrading water quality and, ultimately, the building of the reservoir dam in Halistenkoski Rapids (5 km upstream from the mouth of the river) in 1922 destroyed the original migratory fish populations. In the 1980's, the rehabilitation project of river Aurajoki was started (Kååriå 1996a). It aims to restore specially sea trout populations (Kååriå 1996b, Kååriå and Naarminen 1996, Kååriå 1999) and also other migratory fish species. An essential target was to create a recreational fishing area in the vicinity of the centre of Turku. Fishstocks have been studied mainly by means of the electrofishing method dating from 1984: in total, 38 species have been found in the river. FISHWAY IN HALISTENKOSKI RAPIDS In 1995, a fishway was built along Halistenkoski rapids which was opened in May 1996 (Fig. 1). The fishway features 22 basins with a cross-sectional area of m and an average depth of 1.5 m (see also Rytkonen & Hepojoki 1990). The fishway itself uses m 3 s' 1, while the rest of the water runs over the dam or through the flood gates. The drop of the head is 0.25 m between each basins, with total head being 5.5 m. The vertical slot (width 0.3 m) reaches from the bottom to the water surface. The fishway is equipped with a tracking system which helps to determine the quantity and size of the fish swimming in it. If necessary, the passage up the river from the uppermost fishway basin can be closed. Fish caught in this manner can be controlled with a crane-operated doublebottom, without affecting water flow in the fishway. The presentations of fishway operations benefit tourism and research as well as educational purposes, and more than visitors have acquainted themselves with the fishway during the first three years. One important point of attraction for recreational fishermen in respect to Aurajoki River is the presence of large sea trout. The average weight of sea trout has been more than 3 kg, and nearly every year big trout up to over 10 kg have been caught. Early releasings (in March-April) combined with the use of local broodstock from Aurajoki River have eerted great influence on the homing 64

22 behaviour of the sea trout. Using these stocking methods, it has been possible to create sea trout populations which have been imprinted in the river and which are swimming up to the river via the fishway (Kåariå 1999). For eample, between May and October 1998, a total of 332 adult sea trout (average weight 3.4 kg), 36 adult salmon (average weight 7.2 kg) and 16 adult rainbow trout have been controlled by means of the fishway (Fig. 2). Altogether 16 fish species have been found in the Halistenkoski Rapids fishway (Table 1). REFERENCES Kåariå, J. & Naarminen, M Havsoringar utplanterade tidigt på våren okar fångsterna i Aura å. Fiskeritidskrift for Finland 6: Kåariå, J a. Aura å - å for vandringsfiskar forr och nu. Fiskeritidskrift for Finland 6: Kåariå, J b. Restoration of Sea Trout Population in the River Aurajoki in SW Finland. Coalition Clean Baltic Newsletter 3:5-6. Kåariå, J., Homing Behaviour of Sea Trout (Salmo trutta): Early Spring Releasings in the River Aurajoki (SW Finland) and their Effects in Recreational Fishing. Manuscript. Pitkånen, H Eutrophication of the Finnish coastal waters: Origin, fate and effects of riverine nutrient flues. Publications of the Water and Environment Research Institute. National Board of Waters and the Environment, Finland. 18: Rytkonen, J. & Hepojoki, A Fishways as a part of river rehabilitation woks. Proceedings of the International Symposium on Fishways '90 in Gifu Japan, October 8-10, 1990: Table 1. Fish species found in the Halistenkoski Rapids fishway. With some species, the biggest individuals are presented. 1 Lamprey 2Eel 3 Salmon 4 Sea trout 5 Rainbow trout 6 Bream 7 Vimba bream SBleak 9 White bream 10 Carp HChub 12 Roach 13 Gudgeon 14Miller'sthumb 15 Perch 16 Ruffe Lampetra fluviatilis Anquilla anquilla Salmo salar Salmo trutta Oncorhynchus mykiss Abramis brama Vimba vimba Albwmus albunus Blicca bjoerkna Cyprinus carpio Leuciscus cephalus Rutilus rutilus Gobio gobio Cottus gobio Perca fluviatilis Gymnocephalus cernuus kg 6.7 kg 4.4 kg 6.9 kg

23 Figure l. The Halistenkoski Rapids fishway D t ro ut Figure 2. Sea trouts, salmons and rainbow trouts controlled by means of the fishway between May and October,

24 THE REHABELITATION OF THE VANHANKAUPUNGINKOSKIRAPH3S OF RTVER VANTAANJOKI Juha Laasonen and Jorma Rytkonen VTT Manufacturing Technology P.O.BOX 1705, FIN VTT, Espoo, Finland ABSTRACT The Vanhankaupunginkoski rapids which is located at the mouth of River Vantaanjoki has a long history as a site for water mills and industry. Helsinki was founded in this area in The river was once well known for the salmon and trout stocks. Centralised treatment of waste waters, rehabilitation of spawning and nursery areas and the construction of fishways have helped to restore the migratory fish stocks. The fishladder for salmon was constructed in the mid of 1980's hut its performance was found inadequate for white fish. Now the importance to set white fish (Coregonus lavaretus) back to the River Vantaanjoki has increased, and the white fish is considered as one of the design fishes for the proposed fishway. Etensive fishway studies with numerical and physical modelling techniques were carried out and it was decided to constract new fishway with riffles and pools. The concrete structures of the fishladder have been demolished in the summer of 1998 and the works for riffles and pools will be implemented during winter. The field studies and monitoring of the project will be carried out hi the autumn of 1998 and during year In the year 2000 the migrating fish in the fishway will celebrate the 450* anniversary of City of Helsinki. INTRODUCTION The mouth of the River Vantaanjoki has a long history as a site for water mills and industry. Helsinki was founded in this area hi The oldest mills were constructed hi siteenth century. In 1735 a saw mill was constructed in the eastern branch, and according to old documents it was accused of reducing the number of migrating fish in the river. The water mills were followed by a brick works, brewery, dye works etc. All the activities in the eastern branch were finished in the nineteenth century, and even timber floating was discontinued in At the end of the nineteenth century the City of Helsinki started to design a water works, which resulted in a new dam and a turbine hall with coupled Francis turbines being constructed in the western branch of the river. The height of the dam is about 6 meters. The technical structures of the water works were constructed on an island between eastern and western branch. hi 1972 a new water works were established in Helsinki, and the old site with all the structures were donated to the Technical Museum of Helsinki. Because of the cultural and historical value of the site, the construction of a fishway poses a challenging design project. The area is now under development, and in addition of the ehibition halls of the museum, a variety of activities have been proposed for the old structures. 1 67

25 Fig. l Vanhankaupunginkoski rapids in the summer The demolition work of the eisting fishladder and the overflow weir has been started. In the eastern branch a fish ladder for salmon and trout was constructed in the mid- 1980s. The free-flowing part net to the fishladder, hovever, was narrow and steep for fish to migrate upstream. There are a lot of observations, hovever that Salmon can survive upstream using the natural rapids in optimal conditions. Stronger trout can also pass the rapids, but quite often the discharge of the rapids is too strong for the trout, and espicially for white fish. Furthermore, the salmon like to use the natural stream, and almost all the observed fish in the ladder have been trout. The fishway has found to be suitable for salmon and trout. White fish cannot pass this fishway. VTT Manufacturing Technology attended in this rehabilitation project in The aim of the rehabilitation is to restore the river as a salmon, trout and white fish river. The quality of the river water has been improved considerably since the 1960s, when the river was loaded by both waste waters from nearby municipalities and run off from farmland. Heavy fish stockings have been made in the river mouth and in the river, but due the strong net fishing in the sea area only part of the stocked fish will reach the river again. Some of the spawning and nursery areas for migrating fish were rehabilitated in the upstream part of the river. HYDROLOGY AND WATER QUALITY The catchment area of the River Vantaanjoki is 1,685 km 2 and only 2.5 % of that area is covered by lakes. The variation in flow is considerable. The flood is strong and of short duration. There are times when the discharge is very low, due to the small storage capacity of the lakes upstream. The maimum flood flow during the period has been 317 mvs and the minimum value has been 1,4 m 3 /s. The mean discharge has been 16,9 mvs. Most of the fish migration in the River Vantaanjoki starts in June and lasts until October. The monthly flow variation in that period is shown in Table 1. 68

26 Table l. Monthly variation of the flow in the period month MNQ [m 3 /s] MQ [m 3 /s] June 2,8 5,9 My 2,6 5,8 August 2,8 6,8 September 3,6 8,2 October 5,1 17,2 MHQ [m 3 /s] 13,3 12,9 18,6 22,6 39,8 FISH SPECIES OF THE RIVER Thirty-four fish species, two lamperns (Lampetra fluvialis) and two crayfish species have been found in the River Vantaanjoki. One third of the species have been maintained by planting activities, but most of the fish species will spawn in the river and produce fries. The most common fish species are different roaches. Other typical fish species are perch, pike, ruff, bullhead and burbot. Heavy plantings of salmon and trout have resulted in those species predominating in some stream areas, but at present natura! reproduction will not maintain meir levels without continuous plantings. After the planting of migratory fish both in the mouth of the river and in the river itself, there have been good possibilities to catch salmon and trout from the river. The planting of salmon in the mouth of the river started in the early 1980s. The annual input is now over fries of both salmon and trout. The planting of white fish is of the order of fries annually. REHABILITATION PROJECT Fig. 2. Flow patterns downstream of the rapids The aim of the rehabilitation is to restore the river as a salmon, trout and white fish river. The design philosophy of the fishway studies was to create suitable hydraulic conditions for fish migration and to form continuity of the river. Also e.g. the possibilities for canoe racing were studied and the costs and least work for improving the fish migration conditions were considered. First choice for fishway is natural-like fishway and the second is vertical l l t l t t * * l'l-" i-1-.r-irwh.wr toli l l r slot fishway, because these are suitable for other fish species even for roach. Other fishway types were also considered. Alternative solutions for improving the fish migration were studied comprehensively in Preliminary designs were made for Borland fishway and the modifications in the eisting fishladder were studied in the scale model. The flow patterns downstream of the rapids were calculated by using advanced numerical modelling techniques (Fig. 2). The scale model studies were started in VTT Manufacturing Technology carried out 69